Abstract

Peroxynitrite, superoxide anion, and hydroxyl radical, formed in the iron-catalyzed Fenton reaction, are important mediators of reperfusion injury. In in vitro studies, DNA single stand breakage, triggered by peroxynitrite or by hydroxyl radical, activates the nuclear enzyme poly (ADP-ribose) synthetase (PARS), with consequent cytotoxic effects. Recently it has been demonstrated that PARP play an important role in the development of ischemia and reperfusion of the gut. In the last few years we have evaluated the pharmacological effects of various PARP inhibitors such us: 3 aminobenzamide (3AB), 5 aminoisoquinolinone (5-AIQ) or GPI 6150 in the pathogenesis of splanchnic artery occlusion shock. Splanchnic occlusion shock was induced in rats by clamping both the superior mesenteric artery and the celiac trunk for 45 min, followed by release of the clamp (reperfusion). At 60 minutes after reperfusion, animals were sacrificed for histological examination and biochemical studies. SAO shocked rats developed a significant fall in mean arterial blood pressure, significant increase of tissue myeloperoxidase activity, and marked histological injury to the distal ileum. SAO shock was also associated with a significant mortality (0% survival at 2 h after reperfusion). Immunohistochemical examination demonstrated a marked increase in the immunoreactivity to nitrotyrosine PARP, P-selectin and intercellular adhesion molecule (ICAM-1) in the necrotic ileum. In addition, in ex vivo studies in aortic rings from shocked rats, we found reduced contractions to noradrenaline and reduced responsiveness to a relaxant effect to acetylcholine (vascular hyporeactivity and endothelial dysfunction, respectively). The PARP inhibitors treatment significantly improved mean arterial blood pressure, prevented the infiltration of neutrophils into the reperfused intestine, improved the histological status of the reperfused tissues, markedly reduced the intensity of nitrotyrosine PARP, P-selectin and ICAM-1 in tissue section from SAO-shocked rats and significantly improved mean arterial blood pressure, improved contractile responsiveness to noradrenaline, enhanced the endothelium-dependent relaxations and improved survival. The up-regulation/expression of P-selectin and ICAM-1 in human endothelial cells exposed to oxidative stress (peroxynitrite) or to a pro-inflammatory cytokine (tumor necrosis factor a – TNFa) was also attenuated by PARP inhibitor. In conclusion, our study demonstrates that the PARP inhibitors exerts multiple protective effects in splanchnic artery occlusion/reperfusion shock.

Keywords: PARP, 3-aminobenzamide, 5-aminoisoquinolinone, adhesion molecules, ischemia and reperfusion